1. Field of the Invention
This invention relates to semiconductor memory devices and more particularly to mask ROM devices and methods of manufacture thereof.
2. Description of Related Art
U.S. Pat. No. 5,002,896 of Naruke for "Mask-ROM Manufacturing Method that Enhances Integration Density" and U.S. Pat. No. 5,200,355 of Choi et al "Method for Manufacturing a Mask-Read Only Memory Device" are references showing Mask ROM process/resulting structures, but show neither a code implant performed in a split polysilicon process nor a structure produced by such a process.